What’s Causing This Pain in the Back of My Knee

When you tear a meniscus, you might hear a “popping” sound. At first the injury might not hurt. But after you walk on it for a few days, the knee can become more painful.

What causes pain behind the knee?

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There are many possible causes of pain in the back of the knee. Some are common and less serious, while others require more immediate medical attention.

The knee is a complex joint, and it takes a lot of impact from even simple everyday activities. People can often reduce or prevent knee damage by avoiding impact and strain on the joint.

Treatment for pain in the back of the knee will vary greatly depending on the cause.

Fast facts on pain in the back of the knee

• There are many possible causes of this kind of pain.
• Receiving early treatment for knee pain often prevents the injury from getting worse.
• In some cases, the pain may be due to fatigue or not stretching before exercise.

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It is important to work closely with a doctor to diagnose pain in the back of the knee, as some causes require long-term treatment to heal completely.

Some possible causes of pain in the back of the knee include the following.

Leg cramps

Cramps occur when muscles become too tight. This tightness may be because the muscle is doing too much work without being stretched. If it is stretched and still cramps, the muscle may simply be overused.

Overuse syndrome can affect different areas of the knee. With this condition, a person might also feel a cramp in the thigh or calf near the knee.

The sensation resembles a sudden, painful spasm of the muscle. The pain may last for seconds or minutes and can range from uncomfortable to severe.

Some other possible reasons for leg cramp include:

• dehydration
• infections, such as tetanus
• liver disease
• excess toxins in the blood
• nerve problems

Pregnant people may also experience leg cramps as a normal effect of pregnancy.

Some people who often experience leg cramps may find relief through regularly stretching their calves. Also, they can try shortening their stride to put less strain on the knee and surrounding muscles.

Baker’s cyst

A Baker’s cyst is a pocket of fluid that builds up in the back of the knee, leading to pain and swelling.

Baker’s cysts may not be noticeable at first, as small cysts do not typically cause pain. However, as the cyst grows, it may shift the surrounding muscles or put pressure on the tendons and nerves, causing pain.

Baker’s cysts may grow to about the size of a table tennis ball. People with Baker’s cysts often feel pressure in the back of the knee, which may cause a tingling sensation if the cyst is affecting a nerve.

In most cases, Baker’s cysts are not a cause for concern, but treatment can relieve the symptoms.

Osteoarthritis

Osteoarthritis is a condition that wears down the cartilage of the joints over time. This condition can easily cause pain in the back of the knee.

People with osteoarthritis in the knee may experience other symptoms, such as loss of motion or difficulty bending the knee. Inflammation in the joint may make it stiff and painful. A person may also feel this discomfort in other places around the knee.

Other forms of arthritis that could be causing the pain include autoimmune conditions such as lupus and rheumatoid arthritis.

Runner’s knee

Runner’s knee refers to the wearing down of the cartilage in the knee joint. When the cartilage is gone, the bones of the knee rub together. Typically, this causes a dull, aching pain behind the knee.

Some other symptoms of runner’s knee include:

• the knee giving out or buckling randomly
• weakness in the knee and leg
• restricted movement in the leg and knee
• a crackling or grinding feeling when the knee bends

Hamstring injury

A hamstring injury is a tear or strain in one or more of the muscles in the back of the thigh. These muscles include:

• the biceps femoris
• the semitendinosus
• the semimembranosus

A hamstring strain happens if the muscle pulls too far. It may tear completely from being pulled too much, and this can take months to heal fully.

Hamstring injuries may be more common in athletes who run fast and in bursts, such as those who play basketball, tennis, or football.

Meniscus tears

The meniscus is a piece of cartilage on either side of the knee. Twisting motions while squatting or bending the leg may tear this cartilage. Many people hear a pop when they tear their meniscus.

The pain from a meniscus tear may not show up at first but typically worsens over the next couple of days.

Meniscus tears often cause other symptoms, including:

• loss of knee motion
• weakness and fatigue in the knee and leg
• swelling around the knee
• the knee giving out or locking up when used

Surgery may be necessary if a meniscus tear is severe and does not heal on its own.

Anterior cruciate ligament injuries

The anterior cruciate ligament (ACL) is a band of tissue that runs through the front of the knee joint, connecting the bones and helping keep the knee joint stable.

ACL strains often happen due to sudden stops or changes in direction. Similarly to meniscus tears, a strain in the ACL may cause a popping sound, followed by pain and swelling.

A torn ACL is a well-known, serious injury, often side-lining an athlete for a long time. Torn ACLs usually require reconstructive surgery.

Posterior cruciate ligament injuries

The posterior cruciate ligament (PCL) plays a similar role to the ACL, though it is less likely to become injured than the ACL.

PCL injuries may happen during traumatic events, such as falling directly onto the knee from a height or being in a vehicle accident. With enough force, the ligament may tear completely.

PCL injuries cause symptoms such as:

• knee pain
• stiffness in the knee if bending
• difficulty walking
• swelling in the knee

Completely resting the knee may help a PCL strain heal. However, a severe PCL injury may require surgery.

Deep vein thrombosis

A thrombosis is a blood clot, and a deep vein thrombosis (DVT) occurs when a clot happens in the veins deep within the leg.

Many people who have a DVT feel more pain when they stand up. However, some may feel pain in their leg and knee at most times.

Some other symptoms of DVT may include:

• skin that is red or warm to the touch
• swelling in the area
• fatigue in the affected leg
• prominently visible surface veins

Risk factors for DVT can include carrying excess weight, being older, and smoking. People who lead sedentary lives may also be likely to experience DVT.

DVT needs medication and care, as it can become more serious if the clot breaks loose into the bloodstream.

What’s Causing This Pain in the Back of My Knee?

You may feel pain in the back of the knee after an injury or due to another health condition, such as a cyst or arthritis. More rarely, it can be an indicator of a more serious condition like a blood clot.

The knee is your body’s biggest joint and one of its most injury-prone areas. It’s made up of bones that can fracture or move out of joint, as well as cartilage, ligaments, and tendons that can strain or tear.

Some knee injuries eventually heal on their own with rest and care. Others require surgery or other medical interventions. Sometimes pain is a sign of a chronic condition like arthritis that damages the knee gradually over time.

Here are some of the conditions that can cause pain in the back of your knee, and what to expect if you have one of them.

A cramp is a tightening of a muscle. Muscles in the calves are most likely to cramp, but other leg muscles can cramp up, too — including muscles in the back of the thigh near the knee.

You’re more likely to have leg cramps when you exercise or during pregnancy. Other possible causes include:

• nerve problems in your legs
• dehydration
• infections, such as tetanus
• toxins, like lead or mercury in the blood
• liver disease

When you have a cramp, you’ll suddenly feel your muscle contract, or spasm. The pain lasts anywhere from a few seconds to 10 minutes. After the cramp passes, the muscle may be sore for a few hours. Here’s how to put a stop to the pain and prevent future leg cramps.

Jumper’s knee is an injury to the tendon — the cord that connects your kneecap (patella) to your shinbone. It’s also called patellar tendonitis. It can happen when you jump or change direction, such as when playing volleyball or basketball.

These movements can cause tiny tears in the tendon. Eventually, the tendon swells up and weakens.

Jumper’s knee causes pain below the kneecap. The pain gets worse over time. Other symptoms include:

• weakness
• stiffness
• trouble bending and straightening your knee

The hamstring consists of a trio of muscles that run down the back of your thigh:

• semitendinosus muscle
• semimembranosus muscle
• biceps femoris muscle

These muscles allow you to bend your knee.

Injuring one of these muscles is called a pulled hamstring or a hamstring strain. A hamstring strain happens when the muscle is stretched too far. The muscle can completely tear, which can take months to heal.

When you injure your hamstring muscle, you’ll feel a sudden pain. Injuries to the biceps femoris — called biceps femoris tendinopathy — cause pain in the back of the knee.

Other symptoms include:

• swelling
• bruising
• weakness in the back of your leg

This type of injury is common in athletes who run fast in sports like soccer, basketball, tennis, or track. Stretching the muscles out before play can help prevent this injury from occurring.

A Baker’s cyst is a fluid-filled sac that forms behind the knee. The fluid inside the cyst is synovial fluid. Normally, this fluid acts as a lubricant for your knee joint. But if you have arthritis or a knee injury, your knee may produce too much synovial fluid. The extra fluid can build up and form a cyst.

• pain in and behind your knee
• swelling behind your knee
• stiffness and trouble flexing your knee

These symptoms can get worse when you’re active. If the cyst bursts, you’ll feel a sharp pain in your knee.

Baker’s cysts sometimes go away on their own. To treat a large or painful cyst, you may need steroid injections, physical therapy, or to have the cyst drained. It’s important to determine if an underlying problem is causing the cyst, such as arthritis. If so, taking care of this problem first may result in the Baker’s cyst clearing up.

The gastrocnemius muscle and the soleus muscle make up your calf, which is the back of your lower leg. These muscles help you bend your knee and point your toes.

Any sport that requires you to quickly go from a standing position to a run — like tennis or squash — can strain or tear the gastrocnemius muscle. You’ll know that you’ve strained this muscle by the sudden pain it causes in the back of your leg.

Other symptoms include:

• pain and swelling in the calf
• bruising in the calf
• trouble standing on tiptoe

The pain should subside depending on the size of the tear. Resting, elevating the leg, and icing the injured area will help it heal faster.

The meniscus is a wedge-shaped piece of cartilage that cushions and stabilizes your knee joint. Each of your knees has two menisci — one on either side of the knee.

Athletes sometimes tear the meniscus when they squat and twist the knee. As you get older, your meniscus weakens and degenerates and is more likely to tear with any twisting motion.

When you tear a meniscus, you might hear a “popping” sound. At first the injury might not hurt. But after you walk on it for a few days, the knee can become more painful.

Other symptoms of a meniscus tear are:

• stiffness in the knee
• swelling
• weakness
• locking or giving way of the knee

Rest, ice, and elevation of the affected knee can help alleviate the symptoms and allow it to heal faster. If the tear doesn’t improve on its own, you might need surgery to repair it.

The anterior cruciate ligament (ACL) is a band of tissue that runs through the front of your knee joint. It connects your thighbone to your shinbone and helps stabilize and provide movement to your knee.

Most ACL injuries happen when you slow down, stop, or change direction suddenly while running. You can also strain or tear this ligament if you land a jump wrong, or you get hit in a contact sport like football.

You might feel a “pop” when the injury happens. Afterward, your knee will hurt and swell up. You might have trouble fully moving your knee and feel pain when you walk.

Rest and physical therapy can help an ACL strain heal. If the ligament is torn, you’ll often need surgery to fix it. Here’s what to expect during ACL reconstruction.

The posterior cruciate ligament (PCL) is the ACL’s partner. It’s another band of tissue that connects your thighbone to your shinbone and supports your knee. However, the PCL isn’t as likely to get injured as the ACL.

You can injure the PCL if you take a hard blow to the front of your knee, such as in a car accident. Sometimes injuries occur from twisting the knee or missing a step while walking.

Stretching the ligament too far causes a strain. With enough pressure, the ligament can tear into two parts.

Along with pain, a PCL injury causes:

• swelling of the knee
• stiffness
• trouble walking
• weakness of the knee

Rest, ice, and elevation can help a PCL injury heal faster. You might need surgery if you’ve injured more than one ligament in your knee, have symptoms of instability, or you also have cartilage damage.